大乘起信論裂網疏 2.65

2.65

本覺既即平等法身，離一切妄念相，云何得有二差別相？特以隨染分別，說有始覺；由始覺故，方顯本覺相用，故無生而說生也。

Since original awakening is the equal dharmakāya, free from all marks of deluded thoughts, how could it have two differentiated marks? It is solely in accordance with the differentiation of defilement that initial awakening is spoken of; and it is due to initial awakening that the marks and functions of original awakening are revealed; therefore, where there is no arising, arising is spoken of.